he central theme of our research is idiopathic or unexplained male infertility which affects about 1.5 million American men. For the present proposal we have identified a fertIle control population. and five groups of men with idiopathic male infertility: (a) Husbands of Infertile couples referred to our Sperm Physiology Laboratory (about 650 men/1000 samples per year); (b) Unexplained male infertility (already identified normospermic men with diminished sperm CK-M ratios); (c) Fertile and infertile patients with varicocele; (d) Husbands of 1300 infertile couples in which a detailed data base was developed, including their reproductive history. lifestyle, drug use and other epidemiological characteristics; and (e) Patients who receive medications that affect sperm function. In order to develop improved methods for the diagnosis and treatment of men with idiopathic infertility in the physician's office and in the Andrology laboratory we propose to study: 1) Sperm creatine kinase (CK) activity and CK-M isoform ratios, objective biochemical markers of sperm cellular maturity and fertilizing potential. Within this aim, we will: (a) Isolate the CK-M isoform of human sperm and will generate CK-M specific antibodies for the assessment of maturity rather than morphology of ejaculated sperm. (b) Develop sperm CK antibodies which will not react with seminal fluid CK, in order to directly measure sperm Ck in semen samples by immunotechnology already present in clinical laboratories and in doctors' offices. 2) In line with our hypothesis, which assumes that idiopathic infertility may be caused by isolated deficiencies of acrosome activation in mature sperm, and that in vitro enhancement of sperm function may correct this problem, we will (a) study the rate of both capacitation and acrosome reaction in fertile men and in men with idiopathic infertility; (b) study acrosome activation and the CK parameters in the same sample and (c) examine the possible correlation between sperm CK parameters and acrosome function in the paradigms of the hamster oocyte penetration assay and (ARIC). the Ca- ionophore mediated acrosome response test. 3) Following up on our discovery that hyaluronic acid increases sperm velocity, we will: (a) Study sperm velocity response in a hyaluronic acid "challenge test"; (b) Compare, in a kit available in doctors' offices, sperm progress In cervical mucus with and without hyaluronic acid; and (c) Develop hyaluronic acid beads for the selection of mature, viable sperm for intracytoplasmic injection. 4) Because idiopathic male infertility may arise due to various pathomechanisms, we will compare the diagnostic efficiency of sperm CK-parameters with "strict" sperm morphology, with anilin blue staining, which probes sperm chromatin maturity, and with the hyaluronic acid velocity response test.